CN107614442A - Water treatment and/or remediation methods - Google Patents

Abstract

Describe a kind of method for being used to handle the water of the cationic substance containing one or more dissolvings and/or the anionic species of one or more dissolvings.This method comprises the following steps：The silicate material containing magnesium and/or aluminium is added in water, and the silicate material is dissolved in water by least a portion, so as to which at least a portion magnesium and/or aluminium are leached into water from the silicate material.This method also includes control reaction condition, to reach for being formed in situ layered double-hydroxide the suitable Mg in water：Al ratios, layered double-hydroxide contain the Mg and Al as main matter in LDH lattice；In the LDH that wherein at least one of the cation of the dissolving and/or anionic species manual reduction is formed.In addition, compound containing Mg or compound containing Al are also optionally added to reach suitable Mg：Al ratios.

Description

Water treatment and/or remediation methods

technical field

The present invention relates to methods of treatment and/or remediation of water, including but not limited to natural water, waste water and process water.

The process of the present invention involves all water, other liquids or solutes or solvents or mixtures (whether miscible or immiscible) and solids such as but not limited to natural water, waste water or mineral processing/metallurgical streams and electronic Waste (e-waste) streams, derived from one or more processes including leaching in acidic, neutral or basic reagents or chemical extraction, may typically contain a range of elements (as ions, molecules, complexes , micelles, aggregates, particles or colloids, etc.) and metals or metallic substances or other elements (such as and including metals, metalloids, lanthanides or rare earth elements (REEs), actinides, transuranic metals and radionuclides).

Background technique

Layered double hydroxides (LDHs) are a class of both naturally occurring and synthetically produced materials characterized by positively charged mixed metal hydroxide layers separated by an intermediate layer containing water molecules and various exchangeable anions . LDHs are most commonly formed by co-precipitation of divalent (eg Mg ²⁺ , Fe ²⁺ ) and trivalent (eg Al ³⁺ , Fe ³⁺ ) metal cation solutions at moderate to high pH (Taylor, 1984, Vucel ic et al., 1997, Shin et al., 1996).

LDH compounds can be represented by general formula (1):

M _(1-x) ²⁺ M _x ³⁺ (OH) ₂ A ^n- yH ₂ O (1)

Among them, M ²⁺ and M ³⁺ are divalent and trivalent metal ions, respectively, and An- is the middle layer ion of valence state ⁿ . The x values represent the ratio of trivalent metal ions to the total amount of metal ions, and y represents variable amounts of mesosphere water.

Common forms of LDH include Mg ²⁺ with Al ³⁺ (commonly known as hydrotalcite [HT]) and Mg ²⁺ with Fe ³⁺ (known as phyllite), but other cations include Ni, Zn, Mn, Ca , Cr and La are known. The amount of positive surface charges generated depends on the molar ratio of metal ions in the lattice structure and the preparation conditions as they affect crystal formation.

The formation of HT (the most commonly synthesized LDH, often with carbonate as the main "exchangeable" anion) can be most simply described by the following reaction:

6MgCl ₂ +2AlCl ₃ +16NaOH+H ₂ CO ₃ →Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .nH ₂ O+2HCl

Typically, the ratio of divalent to trivalent cations in hydrotalcites varies from 2:1 to 4:1. Other synthetic routes to form HT (and other LDHs) include synthesis from Mg(OH) ₂ (brucite) and MgO (calcined magnesia) by neutralizing acidic solutions (eg Albiston et al., 1996). This can be described by the following reaction:

6Mg(OH) ₂ +2Al(OH) ₃ +2H ₂ SO ₄ →Mg ₆ Al ₂ (OH) ₁₆ SO ₄ .nH ₂ O+2H ₂ O

A range of metals in various concentrations can also co-precipitate simultaneously, thus forming multimetallic LDHs. HT or LDH were first described 60 years ago (Frondel, 1941, Feitknecht, 1942). Sometimes, they can also occur in nature as auxiliary minerals in soils and sediments (eg Taylor and McKenzie, 1980). Layered double hydroxides can also be synthesized from industrial waste by reacting bauxite slag (red mud) derived from alumina extraction with seawater (e.g. Thornber and Hughes, 1987), as described in the following reaction:

6Mg(OH) ₂ +2Al(OH) ₃ +2Na ₂ CO ₃ →Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .nH ₂ O+2NaOH or by lime and fly from fossil fuels (such as coal-fired power stations) Ash reaction to synthesize (Reardon and Della Valle, 1997).

Within the LDH or HT structure, there are octahedral metal hydroxide sheets with a net positive charge due to the limited displacement of divalent cations by trivalent cations as described above. Therefore, it is possible to replace a wide range of inorganic or organic anions into LDH or HT structures. These anions are often referred to as "interlayer anions" because they fit between layers of hydroxide material. Layered double hydroxides are generally unstable at pH below about 5 (Ookubu et al., 1993), but can act as buffers over a wide range of solution pH (Seida and Nakano, 2002). Layered double hydroxides or HT, and especially those containing carbonate as the main anion, have also been shown to have considerable ability to neutralize a series of inorganic acids (eg Kameda et al., 2003).

Many studies have been conducted to investigate ways to exploit the anion exchange properties of LDHs. These studies have focused on the removal of phosphate and other oxyanions and humic substances from natural materials and wastewater (Miyata, 1980, Misra and Perrotta, 1992, Amin and Jayson, 1996, Shin et al., 1996, Seida and Nakano, 2000). Phosphate is one of many anions that can be exchanged into the mesosphere space of LDH. Laboratory studies of phosphate uptake using synthetically prepared Mg-Al HT and a range of initial dissolved phosphate concentrations showed uptakes of about 25–30 mg P/g (Miyata, 1983, Shin et al., 1996) to about 60 mg P/g The absorption capacity of g is also affected by the initial phosphate concentration, pH (maximum phosphate absorption is close to pH 7), crystallinity and HT chemical composition (Ookubo et al., 1993). The main obstacle to the removal of phosphate from natural and/or wastewater by HT is the selectivity of carbonate to phosphate, where the sequence of selectivity is roughly in the order of CO ₃ ^2- >HPO ₄ ^2- >>SO ₄ ^2- , OH ^- > F ^- > Cl ^- > NO ₃ ^- (Miyata, 1980, 1983, Sato et al., 1986, Shin et al., 1986, Cavani et al., 1991). Many HTs are also synthesized with carbonate as the main anion, thus requiring anion exchange before they are exposed to phosphate. The reduction in phosphate uptake by HT is further reduced when carbonate is also combined with sulfate, nitrate and chloride (as can be commonly found in natural or wastewater) (Shin et al., 1996).

Many recent studies have focused on the formation and study of synthetic LDHs or specific HTs or analogues, and their subsequent reactivity towards a range of anions, especially silicates (e.g. Depege et al., 1996), with the aim of forming polymetallic aluminosilicates, Its potential precursor to clay materials is thought to limit metal mobility and bioavailability (eg Ford et al., 1999). As another precursor of clay mineral analogues, the possibility of co-precipitation of silicate and aluminate anions also exists.

Thus, other structural elements or interlayer ions (both inorganic and organic) can be incorporated to assist in the displacement and/or incorporation of ions from solution, and/or to increase stability. Minerals of the chlorite or phyllosilicate type are subsequently formed from pure Mg-Al or predominantly Mg-Al HT, which may be similar to HT or may be isochemical in composition when compared to HT, or may Has a similar chemistry to HT, where the displacement of some ions is determined by the properties of the added Mg and/or Al or the properties and chemical composition of natural or waste water that may affect the final geochemical composition, crystallinity or mineralogy.

This increased stability of LDH or HT or chlorite-type minerals or other LDH or HT derivatives is also possible by partial or complete evaporation, calcination or vitrification (leading to partial or complete dehydration and partial/total recrystallization) Combined with the above chemical methods to achieve. Using co-amendment with LDH or HT or encapsulating LDH or HT may also be an option to further increase physical or chemical stability.

The International Atomic Energy Agency (the center for international cooperation in the nuclear field, working with member states and various partners around the world to promote safe, secure, and peaceful nuclear technologies) published a report in 2004 summarizing the State of the art in the field of effluents from uranium mines and plants. Importantly, the novelty of the present invention described herein using the addition of chemical compounds to change the chemical composition of the solution to form LDH or HT is illustrated by no similar description or process (IAEA, 2004) for treating effluents from uranium mines sex.

It will be clearly understood that, where a prior art publication is referred to herein, that citation does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or any other country.

Contents of the invention

In one aspect, the present invention provides a method for treating water containing one or more dissolved cationic species and/or one or more dissolved anionic species, the method comprising the steps of:

(a) adding a silicate material comprising magnesium and/or aluminium, to water, and dissolving at least a portion of the silicate material in the water, thereby leaching at least a portion of the magnesium and/or aluminum from the silicate material into the water; with

(b) Controlling the reaction conditions to achieve a suitable Mg:Al ratio in water for the in situ formation/precipitation of layered double hydroxide (LDH) contained in the LDH's lattice Mg and Al as main substances;

wherein at least one of said dissolved cationic and/or anionic species is incorporated into the in situ formed LDH.

Applicants have realized that the addition of magnesium and/or aluminum containing silicates such as Mg containing sepiolite, vermiculite, attapulgite or talc or kaolinite or natural or synthetic minerals such as zeolites or other clay minerals, when at least When a portion of the silicate material is subjected to the dissolution step (step [a]) of the method of the invention, magnesium and/or aluminum ions may be generated into the water. Without being bound by theory, it is theorized that leaching at least some of the magnesium and aluminum ions into the water results in the leached magnesium and/or aluminum ions being absorbed for in situ formation of the LDH material.

There are several advantages to using magnesium- and/or aluminum-containing silicate materials as sources of magnesium and/or aluminum ions for forming LDH materials.

Applicants understand that adding the silicate material to water followed by dissolution of at least a portion of the silicate results in leaching of at least some of the magnesium and/or aluminum ions originally present in the silicate material. However, applicants have unexpectedly discovered that the remaining undissolved silicate material provides nucleation sites to facilitate the in situ formation or precipitation of LDH material, thereby increasing the yield of LDH formed in water.

It is also understood that the undissolved silicate material also acts as an agent to increase the density and/or aggregate particle size of the in situ formed LDH, thereby facilitating the settling and/or dehydration or physical separation and recovery of the LDH in water.

Another advantage provided by the method of the invention is that the undissolved silicate material can also be used in water as an additional cation or anion exchanger. This means that in addition to LDH materials, undissolved silicate materials can contribute to function as adsorbents for ionic species dissolved in water.

The aforementioned silicate materials may also include, but are not limited to, one or more of the following: attapulgite; clinoptilolite; sepiolite; talc; vermiculite, in the form of rocks such as ground granite, greenstone or serpentinite Mineral aggregates or assotiations, overburden, soils, sediments or wastes (for example from alumina refining (red mud) or coal combustion (fly ash)).

In at least some embodiments, the undissolved silicate material from step (a) and the LDH formed in situ in step (b) form an insoluble clay material mixture, wherein the clay material mixture incorporates the at least one or more dissolved cationic species and/or one or more dissolved anionic species. Such mixtures may also be referred to as hybrid clay mixtures.

In one embodiment, the step of dissolving the magnesium and aluminum containing silicate material comprises leaching the magnesium and aluminum from the silicate material under acidic pH conditions. For example, the silicate material may be dissolved by introducing an acidic solution, such as a hydrochloric acid solution and/or a sulfuric acid solution. Applicants have recognized that acid treatment or acid leaching of silicate materials containing both aluminum and magnesium may result in the leaching or release of aluminum and magnesium ions from the silicate material into the water. Thus, in at least some embodiments, performing the dissolution step under acidic conditions can result in leaching of magnesium and aluminum ions into the water. The leached ions can be used to tune the Mg:Al ratio and use Mg and Al ions as building blocks for the in situ formed LDH.

In an alternative embodiment, the step of dissolving the magnesium and/or aluminum containing silicate material comprises leaching the magnesium and/or aluminum from the silicate material under alkaline conditions. Carrying out the dissolution step of silicate material (containing both magnesium and aluminum) under alkaline conditions results in low dissolution of magnesium and relatively high dissolution of aluminum ions into the water. In at least some embodiments, performing the dissolution step under alkaline conditions can result in leaching of at least aluminum ions into the water, which can be used to adjust the Mg:Al ratio, and use the leached aluminum ions as building blocks for the in situ formed LDH.

Furthermore, in at least some embodiments, Si can also leach into the water as a result of the dissolution step of the present invention. Excess leaching of silica may potentially occupy interlayer anion exchange sites within the LDH during formation, or may combine with leached aluminum ions to form other compounds during LDH formation. In some embodiments, the method further includes controlling leaching of silica into water.

In at least some embodiments, the dissolving step includes agitating the silicate material in the water to leach the at least a portion of the magnesium and/or aluminum from the silicate material. Agitation can be performed by one or more methods, such as stirring and/or sonication and/or any other desired means of agitation. It is also contemplated that a series of agitation steps may be utilized to agitate the silicate material. Applicants have recognized that agitation of the silicate material results in increased leaching of magnesium and/or aluminum ions from the silicate material into the water.

In at least some embodiments, the adding step includes adding a mixture comprising the magnesium and/or aluminum-containing silicate material and an additional silicate material. It is important to realize that by carefully combining one or more magnesium and/or aluminum containing silicate materials in the desired ratios, the desired ratio of divalent to trivalent for LDH formation (Mg: Al) changes. As a result, the amount of additional Mg or Al that needs to be added is reduced, which can lead to significant benefits.

In a further embodiment, the step of controlling the reaction conditions comprises adding at least one Mg-containing compound and/or at least one Al-containing compound to achieve a suitable Mg:Al ratio in water for in situ formation of LDH.

Mg or Al dissolved in water may contain leached magnesium and/or aluminum ions obtained from dissolved silicate material, and in at least some embodiments may also contain magnesium and/or aluminum ions, which are subjected to the present invention The method forms part of the dissolved cations in the water.

This recognizes that many naturals or wastewater in particular can include dissolved magnesium and/or aluminum ions. In the present invention, Mg ions and Al ions present in water are absorbed by forming LDH containing Mg and Al as main metal species in a lattice structure of LDH. Advantageously, LDHs can also absorb other ions and greatly fix them into the interlayer space between the crystal lattices. As a result, other ions can also be removed from the water and largely immobilized.

For example, the at least one aluminum-containing compound may comprise an aluminate (Al(OH) ₄ or _{AlO2 -} .2H2O) or aluminum sulfate, aluminum hydroxide or an aluminum-containing organometallic compound.

Other inorganic compounds such as aluminum sulfate (e.g. Al ₂ (SO ₄ )S.18H ₂ O), aluminum hydroxide (A1(OH) ₃ ) or organometallic compounds (e.g. aluminum acetylacetonate C ₁₅ H ₂₁ AlO ₆ ). Preferably these sources of Al will be basic in order to raise the solution pH to a suitable level for LDH or HT formation, but can also be used where the final solution pH or combination of these or other compounds is basic .

In some embodiments of the invention, it may also be necessary to add additional Mg to the water in order to adjust the ratio of Al to Mg in the water to a desired level, thereby obtaining an LDH or ht. This can be achieved by, for example, adding MgO or Mg(OH) ₂ to water. Advantageously, MgO or Mg(OH ₎ also contributes to the desired pH profile suitable for the formation of LDHs such as HT.

In some embodiments of the present invention, it may be necessary or desired to add additional base or acid neutralizing materials to the natural matter or waste water in addition to at least one Mg-containing compound or at least one Al-containing compound. The additional base or acid neutralizing material may be selected from one or more base or acid neutralizing solutes, slurries or solid materials or mixtures thereof such as lime, slaked lime, calcined magnesia, sodium hydroxide, sodium carbonate, bicarbonate sodium or sodium silicate. This list is not exhaustive and other base or acid neutralizing materials may also be added. The addition of the at least one Mg-containing compound or the at least one Al-containing compound to the natural object or wastewater can be done before adding the at least one Mg-containing compound or the at least one Al-containing compound to the natural object or wastewater, or after adding Additional alkaline or acid neutralizing material is added after at least one Mg-containing compound or at least one Al-containing compound is added to the natural matter or wastewater.

In some embodiments of the invention, the order or sequence of adding the various base or acid neutralizing materials to the acidic water, wastewater, slurry or process water may confer certain benefits, as described elsewhere in this specification. For example, the order of addition can confer geochemical and/or operational advantages on the neutralization process and formation of layered double hydroxide (LDH) and other mineral deposits.

Selective partial or total removal of layered double hydroxide (LDH) and/or other undissolved silicate material and/or mineral deposits or slurry components at various stages of the reaction, whether by feeding acidic water It may also be considered advantageous to add various alkali or acid neutralizing materials to various alkali or acid neutralizing materials, or to add acidic water, wastewater or process water to various alkali or acid neutralizing materials as described elsewhere in this specification .

Examples of this include removal of precipitates or existing solids or aggregates, mixtures thereof or co-precipitates prior to introduction of reverse osmosis to remove some or all of the remaining solutes or evaporation. This removal of layered double hydroxide (LDH) and/or other mineral deposits (including undissolved silicate), whether by adding various alkali or acid neutralizing materials to acidic water, waste water or process water, or adding various alkali or acid neutralizing materials as described elsewhere in this specification Acid water, waste water or process water.

In some embodiments of the invention, partial or total removal of water or other solvents or miscible or immiscible solutes (e.g., by partial or total evaporation or distillation) may be used to increase one or more dissolved colloids or The concentration of particulate constituents or additionally added constituents such as Mg and/or Al (eg to adjust a suitable Al to Mg ratio) is such that the concentration is increased to a sufficient extent to initiate LDH formation.

The present invention, in at least some embodiments, also relates to water and water streams, including process waters that may contain little or no Mg and/or Al or be dominated by other dissolved cations and/or anions. (such as those originating from some acid sulfate soils, industrial processes or nuclear power plants, weapons or research facilities). It is worth noting that not all water (eg, process or wastewater) has a major ion chemistry suitable for the formation of LDHs or specific types of LDHs such as Mg-Al HT or similar compositions. Therefore, it may be necessary to adjust this chemical composition to form LDHs or more specifically Mg-Al HTs. The adjustment of the chemical composition of the solution includes the step of adding silicate material in the manner described in step (a), and may also include the addition of one or more reagents, such as Mg and/or Al containing reagents to achieve a suitable Mg :Al ratio to promote the in situ formation of LDH.

In some embodiments, at least one dissolved anion in water from a stream, such as a process stream, may comprise a complexing anion such that at least one of the complexing anions is inserted into the interlayer of the in situ formed LDH, and One or more dissolved cations are incorporated into the crystal structure or matrix of the LDH material. Preferably, the method may further comprise the step of controlling the pH level in the water, thereby controlling the form of complexed anions.

It will be appreciated that cations such as metal cations may be incorporated into the metal oxide layer of the LDH forming the crystal structure or matrix. Applicants have also recognized that some metallic constituents, particularly metals such as uranium (or vanadium or chromium in other embodiments) often exist as large sized oxygen-containing cations such as ^UO22+ _that cannot be accommodated in the crystal structure or matrix. Applicants have found that by adjusting or controlling reaction conditions such as pH conditions and/or adding reactants, etc., such large-sized oxycations such as UO ₂ ²⁺ can be used to preferentially form one or more complex anionic species, such as any UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- , UO ₂ ²⁺ -SO ₄ . For example, at lower pH, UO ₂ ²⁺ -SO ₄ complexes (such as UO ₂ (SO ₄ ) ₃ ^4- ) can predominate, while at moderate to higher pH, UO ₂ ²⁺ -CO ₃ ^2- anionic complexes (eg UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- ) may predominate. Given this morphology of uranyl ions (UO ₂ ²⁺ ) as anionic complexes, these anionic complexes preferentially partition into the anionic interlayer of the LDH material. Thus, if an aqueous solution contains metals such as Cu, Mn, Ni, Pb, Zn, and rare earth elements (REEs; 15 metallic elements with atomic numbers from 57 to 71; REEs are often described as part of the lanthanides, for convenience , often expressed as a mixture of Ln ³⁺ ) and uranium, the method of the present invention will separate uranium from the remaining metals, metalloids and rare earth elements by preferentially forming uranyl complex anion complexes, the uranyl complex anion The complexes will be inserted into the interlayer of the LDH and at least some metals and rare earth elements will be incorporated into the crystal structure of the LDH. For example, REEs predominantly Ln ³⁺ cations (Ce in +3 and +4 and Eu and +2 and +3 oxidation states) are strongly partitioned into the predominant metal hydroxide layer of the LDH material, displacing the other +3 cations Such as Al and Fe. As a result of the method according to the invention, REE is for example contained within the metal hydroxide layer of the LDH and valuable uranium is contained as an anionic complex within the LDH interlayer.

The current embodiment also results in the formation of LDH materials that can typically contain over 30% U and 0-50% REE. Such resulting quantities of uranium and rare earth metals are typically 100-300 times the typical ore grade for these elements, resulting in a substantial enrichment of valuable items. Another significant benefit provided by the present invention is that the process results in efficient separation of potentially problematic ions such as Na, Cl and _SO or other additives or components from mineral processing or aqueous streams, thus potentially facilitating simpler processing , further enrichment, recovery or purification). Yet another advantage of at least some embodiments of the present invention is the production of cleaner effluents that can potentially be reused in mineral processing or other field applications or other operations with no (or minimal) additional treatment.

The present invention therefore also provides, in at least some embodiments, a method or process for the treatment of process water for recovering selectively separated components in water provided as an aqueous solution, wherein by subjecting the LDH from step (b) to further Recycling process step, different constituents have been absorbed by LDH by different absorption mechanisms (eg uranium in the middle layer of LDH versus REE in the crystalline structure of LDH or metallic oxide layer). Various recycling processing steps that may be used have been described in detail in the preceding paragraphs of this specification.

In some embodiments, the method includes recovering LDH from the aqueous stream prior to subjecting the separated LDH from step (b) to a recovery treatment step. This recovery of LDH can be performed by recovery means such as sedimentation, flocculation or filtration.

In one embodiment, the method further comprises the step of controlling the pH level of the aqueous solution to control the speciation of complex anions. Applicants have found that the morphology of the anion complex can be appropriately adjusted or controlled by adjusting the pH conditions. For example, at lower pH, UO ₂ ²⁺ -SO ₄ complexes (such as UO ₂ (SO ₄ ) ₃ ^4- ) can be preferentially formed, while at moderate to higher pH conditions, UO ₂ can be predominantly formed ²⁺ -CO ₃ ^2- anionic complexes (eg UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- ).

The separated LDH can be processed to recover components therefrom. In some further embodiments, the recovery treatment step may be performed by introducing the separated LDH into an ion exchange solution to cause ion exchange to occur, thereby exchanging the complexed anions of the metallic constituents in the intermediate layer of the LDH with the ion exchange The anions in the solution undergo ion exchange. In this way, by performing an ion exchange step, the complexing anions of the metallic solution go into solution. It will be appreciated that such an ion exchange step involves an ion exchange solution having at least one substituent anion such that the substituent ion displaces at least some of the intercalating or complexing anions through an ion exchange mechanism, thereby causing the anion or complexing anion to change from The LDH interlayer is released into the ion exchange solution. Simultaneously, the intercalating or complexing anions of the metallic constituents are released from the interlayer of the LDH and other metals present in the crystal structure or matrix of the LDH (e.g. REE/metals) remain incorporated into the crystal structure or matrix of the LDH material.

Applicants have found that recovery of LDH from step (b) followed by an ion exchange process occurs when the initial aqueous solution in step (a) comprises a leach solution with a high salt concentration such as that used in a leach process for the recovery of uranium is particularly beneficial as it has been found to be difficult to achieve optimal ion exchange efficiency in such leach solutions such as mining effluents. Employing the method described in some embodiments comprising the step of isolating the LDH from step (b) and as described above results in a higher ion exchange efficiency resulting in better separation of intercalated metallic components from the LDH.

In a further embodiment, the ion exchange step further comprises controlling the pH conditions to facilitate displacement of anions or complex anions from the interlayer and/or to promote species formation of preferred types of anions or complex anions relative to other anions or complex anions . For example, a strong base can be added to displace UO ₂ ²⁺ -SO ₄ or UO ₂ ²⁺ -CO ₃ complexes by OH anions by increasing the pH. It will be appreciated that such recovery processing steps include recovery of uranium (in the form of the uranyl complex anion) back into the aqueous solution, even though the REE remains incorporated into the LDH crystal structure. Alternatively, it is also possible to add a strong acid to lower the pH so that the charged or neutral UO ₂ ²⁺ complexes are displaced from the interlayer of LDH. Here, continued acid addition can also sufficiently break down the LDH crystal structure to release REEs or other metals or elements.

In some embodiments, substituent reagents may comprise one or more of the following: nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), or a range of other complexing agents such as crown ethers or other organic or ( complexed) inorganic ligands, and/or wherein the substituent reagent has significantly more electronegativity relative to the complexing anion intercalated in the LDH material, thereby causing the substituent reagent such as EDTA and/or NTA to complex the anion Displaced from the middle layer.

In a further embodiment, the recovering step further comprises isolating the LDH material after the ion exchange step is complete. It will be appreciated that isolating the LDH material after completion of the ion exchange step results in an isolated LDH material comprising incorporated metallic cations or REEs present in the crystal structure of the isolated LDH material. Incorporated metallic cations or REEs from isolated LDH can be recovered by methods such as thermal treatment or thermal decomposition of the isolated LDH material, resulting in the formation of a collapsed or metastable material.

In further embodiments, the method may include adding additional additives (eg, silica) to the LDH material prior to or during thermal treatment or thermal decomposition. Preferably, the method may include controlling the ratio of the additional additive to the LDH material to selectively control the formation of oxide material upon heat treatment or thermal decomposition.

Additives such as silica can also be added to the LDH before or during the thermal treatment or thermal decomposition step, in forms ranging from crystalline silica (e.g. quartz), amorphous or chemically precipitated silica, silicic acid, organic forms including Tetraethyl silicate (te) or silica added to the LDH interlayer.

It is important to realize that, in addition to recycling LDH material, LDH can also be used to recover and undissolved silicate material from step (a) can also be used. Controlling the ratio of silica to LDH and/or controlling the temperature of the heat treatment can lead to a series of reactions between the added form of silica and LDH which lead to the formation of a series of materials such as minerals such as (or in addition to) spinel and square Magnesite) pyroxenes such as enstatite, olivine including forsterite and other minerals including silica converted to high temperature forms including cristobalite.

It will be appreciated that by varying the amount of one or more forms of silica or other elements relative to LDH (by controlling the ratio of silica to LDH material), different ratios or series of minerals can be formed as a heat treatment step the result of. This method comprising additives as described above is particularly advantageous for two reasons. A first advantage is that secondary mineral oxides such as metallic silicates or pyroxenes can be formed, which can constitute suitable long-term reservoirs for a range of pollutants, including radionuclides. A second advantage is that a given selected element can be partitioned into the material formed as a result of heat treatment (determined by the composition of the LDH and the type and proportion of additives) which can facilitate the selective recovery of the contained in Specific elements in selected minerals. The silica may be replaced by other additives in other embodiments, and the above embodiments are by no means limited to the addition of silica.

Thus, the addition of a silicate material in step (a) of the present invention may also facilitate the recovery of one or more dissolved species (cationic or anionic) from the LDH material.

In some alternative embodiments, the isolated LDH may be subjected to a dissolution step, wherein the isolated LDH is dissolved in a dissolution solvent such as an acid, which results in the release of intercalated complexing anions and metal cations from the crystal structure of the isolated LDH to the dissolved in solvent. According to step (b) capturing the metallic species from an initial aqueous solution containing a low concentration of the metallic species in the LDH material, isolating the LDH material, and then redissolving the separated LDH in the dissolving solvent, resulting in a solvent having a relatively high concentration level of metallic species (compared to the low concentration level of the initial aqueous solution). It should be recognized that the recovery of metallic species from solutions containing relatively high concentration levels of metallic species is more desirable and cost-effective, and thus provides the artisan with the opportunity to use conventional metallurgical recovery methods that would otherwise be critical to It would be ineffective to capture trace amounts of metallic species present in the aqueous solution as used in step (a) in at least some embodiments of the present invention. Thus, this embodiment has significant commercial advantages by providing a viable method or process for the recovery of metallic species from aqueous solutions having low concentrations of metallic species.

In an alternative embodiment of the method, ion exchange of the intercalating complex anion may not be performed. Instead, the LDH obtained from step (b) comprising the intercalated complex anion and incorporated metal(s) and other materials can be isolated and subsequently subjected to a heat treatment process as described above. Such a heat treatment process initially leads to collapse of the LDH material, resulting in a loss of the layered structural properties of the LDH material, and subsequently to recrystallization of the LDH material. Specifically, heat treatment and recrystallization of the collapsed LDH results in the formation of a first oxide material comprising a metallic component and a second oxide material comprising one or more of such other metals. For example, the applicants have unexpectedly discovered that calcination of LDHs comprising intercalated uranyl complex cations and rare earth metals incorporated into the crystal structure produces the first crystalline oxide material in the form of periclase incorporating a proportion of uranium and A second crystalline oxide material in the form of spinel oxide incorporated into other items such as REEs.

In a further embodiment, the heat treatment may be performed under substantially reducing conditions in order to reduce the presence of intercalating complexing anions within the interlayer of the LDH material obtained in step (b). For example, during heat treatment of LDHs containing intercalated uranyl complex anions, the heat treatment can be performed under anoxic (such as N ₂ ) or reducing (such as CO or C) conditions to form reduced U minerals, such as to produce Pitchblende (UO ₂ ). _In some alternative embodiments, other reagents may be added to form UF6 as the gas phase to aid in the separation and recovery of U or specific U isotopes.

In some additional embodiments, the method can include optimizing the crystal structure or matrix of the LDH material to selectively incorporate one or more of the other metals into the crystal structure or matrix of the LDH. For example, optimization can be performed by introducing additives to the aqueous solution, such as carbonates in alkaline liquids, to adjust the crystal structure of the LDH or the uptake of selected or specific rare earth elements in the matrix. Without being bound by theory, theoretically, given the increased affinity of medium to heavy REEs for carbonate or bicarbonate, the amount/morphology of bicarbonate/carbonate in aqueous solution could potentially confer on LDH materials (e.g. hydrotalcite) Certain selectivity.

In one embodiment, the predetermined metallic constituent comprises uranium or vanadium, and wherein one or more of the other metals comprises REE. As previously mentioned, complex anions [anions] may include uranyl complex anions such as but not limited to: UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- , UO ₂ (SO ₄ ) ₃ ^4- , VO ₂ (OH) ^2- , VO ₃ OH ^2- , V ₁₀ O ₂₈ ^6- , Cr ₂ O ₇ ^2- . In at least some embodiments, the pH of the solution determines the speciation of the uranyl complex anion.

In one embodiment, intercalated uranyl complexes can be displaced from the interlayer of LDH by the ion exchange procedure described in the previous section by adding substituent reagents such as EDTA, NTA, crown ethers, and the like.

In an alternative embodiment, the LDH material may be subjected to a heat treatment step such that the heat treatment results in thermal decomposition of the LDH material to recrystallize into a first crystalline oxide and a second crystalline oxide such that uranium is incorporated into the first metal oxide, and One or more REEs are incorporated into the second crystalline oxide. Preferably, the heat treatment may be performed under substantially reducing conditions for reducing the uranyl ion from the +6 to the +4 oxidation state or a mixture thereof.

In at least some embodiments, the method comprises the steps of contacting the isolated LDH material with an aqueous solution to dissolve at least a portion of the LDH material into the solution, thereby obtaining LDH dissolved in the solution and then controlling the reaction conditions in the aqueous solution for In situ precipitation of LDH material from dissolved LDH material such that complexing anions are intercalated within the interlayer of the in situ formed LDH material and wherein one or more other cations are incorporated into the crystal structure or matrix of the in situ formed LDH material middle. Preferably, the step of dissolving LDH in the aqueous solution comprises controlling the pH of the aqueous solution at a pH level preferably less than 7, and more preferably less than 5, and even more preferably less than 3. In situ precipitation of LDH from dissolved LDH components can be performed by controlling the reaction conditions in the aqueous solution, including controlling the pH of the aqueous solution at a pH level preferably greater than 8.

It is within the scope of the invention that any feature described herein may be combined in any combination with any one or more other features described herein.

Reference to any prior art in this specification is not and should not be taken as an acknowledgment or any form of suggestion that such prior art forms part of the common general knowledge.

Description of drawings

Figure 1 depicts Al/Si and Mg/Si produced by 1M HCl and 1M NaOH after stirring (1-4 hours) and sonication + stirring (1 hour) of filtered clay and zeolite solutions according to an embodiment of the present disclosure. Molar ratio of Al. The red line indicates an Al/Si molar ratio of 0.5 and a Mg/Al molar ratio of 3 (see text).

Figure 2 depicts the X-ray diffraction (XRD) spectrum of a sepiolite/white clinoptilolite-hydrotalcite nanohybrid. Note the peaks corresponding to the sepiolite and clinoptilolite precursors and the characteristic hydrotalcite (light blue)/Mg-Al hydroxide (pink) at Peaks are reached at θ of 13 and 26 degrees.

Figure 3 depicts the phosphorus uptake capacity of a series of clay/zeolite nanohybrid materials synthesized in this study.

Figure 4 is a schematic flow diagram of a method of separating one or more metallic objects in an aqueous solution by employing a method according to a preferred embodiment of the present invention.

Figure 5 represents the morphology diagram of the system UH2O _{- SO4} - _CO3 from pH 2-10 in equilibrium with the atmosphere.

detailed description

The following text describes one or more embodiments by way of example in accordance with the invention.

Raw materials are obtained from industrial and commercial sources, mainly aluminosilicate clays containing Mg-Al or Al (e.g. vermiculite, attapulgite, sepiolite, talc kaolinite) and zeolites (white and pink zeolites). These clays and zeolites were used as sources of raw materials (mainly Al and Mg) during acid and base dissolution experiments enhanced with sonication.

The initial batch decomposition reaction was done in both acid and base and additionally using agitated aluminosilicate including sonication. The results of the ICP analysis are given in Table 1 and Figure 1 to quantify the extent of dissolution due to acid or base combined with agitation (1-4 hours) or sonication + agitation (1 hour). These results suggest that the substantial Mg and Al release required for hydrotalcite synthesis (preferably >3:1 Mg/Al molar ratio) can be obtained from clays or zeolites during acid extraction. Additionally, some clays such as sepiolite (Table 1) yield high concentrations of Mg and Al and high Mg/Al molar ratios. All clays and zeolites showed inconsistent dissolution under acidic conditions where the Mg/Al and Al/Si ratios were higher in the solute than in the solid. In contrast, under basic conditions, any inconsistent dissolution is masked by secondary precipitation reactions.

Table 1. Geochemical composition of filtered solutions resulting from digestion with 1M HCl or 1M NaOH after stirring (1-4 hours) and sonication+stirring (1 hour) of clay and zeolite suspensions.

Importantly, using the combination of sonication + stirring significantly enhanced the dissolution of Mg and Al relative to stirring alone. During acid digestion, depending on the chemical composition and purity of the clay or zeolite, large amounts of Si and other elements such as Fe and Ca may also be released. This is undesirable because excess silica could potentially occupy interlayer anion exchange sites within the LDH or HT during formation, or could combine with Al to form other compounds during LDH or HT synthesis. In particular, as shown in Figure 1, an Al/Si molar ratio <0.5 is required. In addition, a large amount of Fe can lead to the substitution of one or both of Mg and Al in the LDH or HT structure. If Fe is present in sufficient amounts, this can lead to the formation of an unstable patina.

As expected, alkaline dissolution using stirring or sonication+stirring yielded significantly different solution compositions in which the dissolution of Si was enhanced compared to that of Al, while Mg was low as it may have acted as brucite-Mg(OH ) ₂ and precipitated. Although excess silica is generally undesirable in the formation of LDH or HT as described above, there is the possibility of using residual clay or zeolite after dissolution as a substrate for LDH or HT nucleation.

In the presence of high Si, this can occupy at least a part of the anionic interlayer of the LDH or HT structure. This property can be exploited if calcination is required to form other high temperature phases as described elsewhere.

Further clay dissolution experiments _were performed with _H2SO4 instead of HCl to investigate the effect, if any, of using a different acid. These results are given in Table ₂ and illustrate that relatively less dissolved Si is produced in the presence of _H2SO4 , resulting in a lower Al/Si ratio. As mentioned above, this is believed to be important in the synthesis of LDH or HT from solutions resulting from the dissolution of clays or zeolites. Also, using _H2SO4 instead of HCl, the Mg/Al ratio generally increases _.

Table 2. Al, Si and Mg and Mg/Al and Al/Si concentration ratios in solutions resulting from digestion of clay and zeolite suspensions with 1M _H2SO4 and 1M HCl using sonication ₊ stirring (1 hour).

_On the basis of the above dissolution experiments and supplementary experiments using _H2SO4 instead of HCl, a series of clays and zeolites were used to synthesize nanohybrid materials. In addition, aluminates are also used as sources of additional Al and as neutralizing agents. Table 3 presents a list of the as-prepared nanohybrid materials and their P absorption capacity.

Table 3. Phosphorus uptake capacity of a series of clay/zeolite nanohybrid materials synthesized in this study.

Use the following equation to determine the mixing ratio of the solutions both in the presence and absence of residual clay or zeolite solids:

v ₁ /v ₂ ＝(r[Mg] ₂ –[Al] ₂ )/([Al] ₁ –r[Mg] ₁ )

where v1 and v2 are the volume ratios _of the _two clay or zeolite solutions required to give r, r the desired Mg;Al ratio in the final solution (3 in this case), and [Mg] ₁ , [Mg] ₂ and [Al] ₁ and [Al] ₂ are the concentrations of Mg and Al in solutions 1 and 2, respectively. The calculated target Mg/Al molar ratio was 3 when adding aluminate.

Mineralogical (XRD) analysis of the nanohybrid material is depicted in Figure 2, which indicated the presence of hydrotalcite in addition to residual clay or zeolite minerals that acted as scaffolds for hydrotalcite nucleation and precipitation.

The significance of the examples presented here lies in the synthesis of a new class of materials using a novel preparation method that utilizes elements contained in commercial clays to produce Nanohybrids of LDH. The beneficiation process adds significant utility and value to commercially mined clays and zeolites, as demonstrated by the high P uptake (as phosphate) achieved. The high P-absorption suggests that these materials can also be used to remove other simple or complex anions, such as uranyl carbonate complexes, from solution.

Referring to the flow diagram shown in Figure 4, an ore body containing multiple metallic constituents such as uranium and REEs may be introduced into an aqueous leach solution to obtain an enriched leach solution or aqueous stream. Some metallic components such as uranium can form complex anions in solution, such as the uranyl anion complexes described in the previous section. Some other metallic constituents, especially constituents such as REEs, can often form cations in aqueous solutions. The liquid phase of the enriched leach solution containing dissolved anions and cations can be separated from undissolved solids and directed to the reaction step. The reaction step may include steps such as controlling the pH to determine the morphology of the uranyl complex as shown in FIG. 5 . The reaction step may form a complex anion containing a metallic component such as uranium. The reaction step may be followed by an LDH formation step or an optional LDH addition step or LDH addition and pH cycling to induce partial dissolution and subsequent reformation of LDH.

In the LDH formation step, additives such as divalent additives such as MgO can be added in combination with trivalent additives such as soluble alumina salts in specific ratios and at a suitable pH (basic pH) to facilitate the formation of LDH materials in solution. bit formation. Such an LDH formation step also results in the intercalation of an interlayer of complex anions (eg, uranyl complex anions) of the in situ formed LDH material. Metallic cations are also incorporated into the metal oxide layer of the in situ formed LDH material, thereby forming part of the crystal structure or matrix of the LDH. This separation of metallic species is based on the different absorption mechanisms of different ions provided by the in situ formed LDH materials.

As previously described, the LDH formation step can be replaced or supplemented by an LDH addition step in which preformed LDH material can be added to a solution containing complexing anions (uranyl complexing anions) and metallic cations. The step of adding pre-formed LDH material also results in the intercalation of an interlayer of complex anions (eg, uranyl complex anions) of the LDH material. This step may also include controlling the pH so that a portion of the LDH can be dissolved initially at pH less than 9 and as low as pH 1 for the specified period of time required to produce a sufficient degree of LDH dissolution, followed by increasing the pH to promote LDH The material reforms in situ. During this reformation step, other cations such as REE cations may be incorporated into the metal hydroxide layer to replace the original cations in the initially added LDH. During this process, some anions, especially those composed of uranyl anion complexes, can also be substituted into the interlayer of LDH materials. Note that other techniques can also be used in the solubilization or reformation steps, including (ultra)sonication or addition of other solvents or reagents as desired.

The LDH material containing intercalated complex anions and obtained from the LDH formation step or LDH addition step can be separated by processes such as settling, flocculation, filtration, cyclone separation or other known separation methods. The separated LDH material may then be subjected to a further process for recovery of the intercalated complex anion (uranyl complex anion), such as an ion exchange process, according to the steps described in the preceding part of the specification. Alternative methods of recovering intercalated metallic components can also be used according to the process steps detailed in the previous sections. As previously stated, the recovery treatment step may not be limited to recovery of intercalated metallic components such as uranyl complex anions, but may further include recovery of metallic cations such as REE incorporated into the LDH matrix during the LDH formation step.

The presently described invention exploits the different absorption mechanisms of different metallic ionic species as a means of separating metallic species. In the present invention, metallicity is recovered from LDH by intercalation of at least one metallic component (formed in situ or added to solution) into the interlayer (e.g. uranyl complex anion) of LDH and subsequent recovery steps components to achieve the desired separation and recovery.

Example

Example 1

In a first exemplary embodiment (Example 1), the method can be used for processing uranium-containing ores. Common in uranium-bearing ores is the presence of a range of other elements in addition to uranium. Other elements may include elements such as As, Se, Cu, and rare earth elements (REE-Ln ³⁺ , including La-Lu+Sc+Y). Extensive work undertaken by the applicants demonstrated that REEs exist predominantly as Ln ³⁺ cations in the +3 oxidation state. Cerium exists in the +3 and +4 oxidation states. Europium exists in the +2 and +3 oxidation states. In this exemplary method, a uranium-containing solution from leached uranium ore is contacted with an LDH material.

Intercalation of uranyl complex anions can be achieved in two different ways. In a first possible way, uranyl complex anions will readily intercalate into the interlayer of LDH material added to the solution. However, utilizing such a method does not result in REE absorption into the matrix or crystal structure of the LDH material added to the uranium.

In a more preferred manner, the LDH material added to the uranium-containing solution is dissolved in the uranium-containing solution by lowering the pH of the solution to less than 3. Lowering the pH level causes the LDH material to dissolve, resulting in the release of divalent and trivalent cations (forming the metal oxide layer of the LDH material) into solution. After dissolving the LDH material, the pH is increased to provide basic reaction conditions in solution. Providing such basic conditions results in reformation of the LDH material due to precipitation of the LDH material in solution. During reformation of the LDH material, divalent and trivalent cations dissolved into solution (as a result of the initial dissolution step) precipitate to form the metal oxide layer of the reformed LDH material. During the reformation step, at least some REE cations were also incorporated into the crystal structure of the reformed LDH material. Anionic uranyl complexes were also inserted into the interlayer of the reformed LDH material. It is important to realize that this can occur in reformed LDHs since the divalent to trivalent ratio of the metal in the primary metal hydroxide layer of the LDH can typically vary between 2:1 and 4:1. The change in ratio due to the incorporation of other cations from solution still allows the formation of stable LDH.

During this process, REEs were shown to be strongly partitioned into the main metal hydroxide layer of the reformed LDH material, displacing other +3 cations such as Al and Fe present in the initially added LDH material. Unlike REE cations, uranyl ions (which are known to exist in solution as UO ₂ ²⁺ oxygenated cations) are considered too large to replace the +2 cations such as Mg2+ typically present in the metal hydroxide layer of LDH materials Alkaline earth metals and transition metals. As shown in Figure 2, under low pH conditions, anionic uranyl complexes, especially UO ₂ ²⁺ -SO ₄ complexes (eg UO ₂ (SO ₄ ) ₃ ⁴⁻ ) are formed. At moderate to high pH, UO ₂ ²⁺ -CO ₃ ^2- anionic complexes (e.g. UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- ) can dominate. Considering this morphology of UO22+ as anionic complexes, these uranyl anionic complexes preferentially partition into the anionic interlayer of LDH. As a result, the method of Example 1 provides the following advantages:

Valuable REEs are contained within the metal hydroxide layer of LDH

• Valuable U is contained in the LDH interlayer as an anionic complex. These two items of value, U and REE, are not only separated from each other in terms of the way they are combined in the initial solution, but are also separated from other components, including some contaminants, salts, or ions (which may otherwise interfere with U or REE). The separation of REE recovery process) is very beneficial to the subsequent separation, recovery and purification.

• Production of solid LDHs, which can typically contain over 30% U and 0-50% REEs, typically 100-300 times the typical ore grade for these elements, allowing substantial enrichment of items of value.

• Efficient separation of potentially problematic ions such as Na, Cl and SO ₄ or other additives from mineral processing streams (possibly simpler processing, further enrichment or recovery).

• Produce cleaner effluents that can potentially be reused in mineral processing or other sites or operations, with no (or minimal) additional treatment.

In addition to the above, several methods can be used to recover the item of interest (as described above) based on the separation of the obtained item, taking into account the different distribution or separation of U and REE. Recycling of one or more items can be effectively performed by one or more of the following further steps:

• Addition of a strong base to displace the ^UO22+ _{-SO4 complex} by the OH _anion , or lower the pH so that the less charged or neutral UO2 complex is displaced from the LDH interlayer.

• Other complexing ligands or other anions (eg NTA, EDTA) can be added to the LDH to displace the UO2 _- complex and form a new NTA, EDTA complex.

• Addition of other chemical agents such as phosphates, vanadates or inorganic or organic peroxides or combinations thereof to initiate uranium precipitation.

• Partial or complete dissolution of U, REE metal-containing LDHs by addition of acid and recovery of components by conventional means.

Addition of reducing agents, oxygen deficiency or gases (e.g. CO) to reduce uranyl complexes (U+6 oxidation state) to U (+4 oxidation state), e.g. as UO2 for charge _- based elimination with carbonate The uranyl complexes and allows recovery of U in the +4 oxidation state. Such recovery methods may include physical (eg sonication) or additional chemical (solvent-based) delamination of LDH to recover reduced U or apply other physicochemical methods as desired.

• Other isolation methods, which may include calcination, such that upon heating, typically in the range of 100-1200°C, there will be collapse and recrystallization of the LDH layer, resulting in the formation of discrete or closely intergrown mineral phases such as spinel and periclase. These phases (due to their chemical composition and crystal structure) may accommodate one of the various elements of interest, or consideration of the different physicochemical properties of the mineral phases formed by calcination may provide increased recovery opportunities for specific elements.

The stabilization methods described herein may also find application in the nuclear energy or weapons industries to assist in the containment of uranium-containing material or waste including transuranic elements or daughter radionuclides.

Example 2

In a second exemplary embodiment (Example 2), the method of the present invention may be used in processing uranium-containing ores, wherein LDHs may be formed in situ in mineral processing or metallurgical streams comprising uranium-containing ores. A stream of uranium-containing ore is typically fed with one or both of Mg and Al-containing compounds to achieve the desired Mg/Al ratio in the stream, which results in the precipitation of LDH such as hydrotalcite. As explained in Example 1, uranium-containing ores include a range of other elements present in addition to uranium, including heavy metals, metalloids and/or REEs. In situ formation of LDH materials also results in the incorporation of cations such as Ln ³⁺ cations and/or Ce 3+ and Ce 4+ and/or Eu 2+ or Eu 3+ oxidation states. The in situ formation of LDH also resulted in REE cations shown to be strongly partitioned into the main metal hydroxide layer of LDH. As mentioned previously, since uranium exists as an oxygen-containing cation generally called uranyl (UO ₂ ²⁺ ) cation, uranyl ions are too large to replace +2 cations such as Mg 2+ into LDHs. Alkaline earth and transition metals are usually present in the metal hydroxide layer of LDH. Again, under low pH conditions, anionic uranyl complexes are formed, especially UO ₂ ^2+- SO ₄ complexes (eg UO ₂ (SO ₄ ) ₃ ⁴⁻ ). At moderate to higher pH, UO ₂ ^2+- CO ₃ ^2- anionic complexes (eg UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ (CO ₃ ) ₃ ^2- ) can dominate. Considering this morphology of UO ₂ ²⁺ as anionic complexes, these uranyl anionic complexes preferentially partition into the anionic interlayer of the in situ formed LDH. The method described in Example 2 also provides one or more of the several advantages of the method of Example 1 as outlined above. The item of interest may also be recovered by one or more of the further recovery steps outlined in Example 1.

Example 3

In a third exemplary embodiment (Example 3), the method of the present invention can be used to process uranium-bearing ores, wherein LDHs can be formed in situ in alkaline mineral processing or metallurgical streams comprising uranium-bearing ores.

A uranium-containing ore stream is typically fed with one or both of Mg and Al-containing compounds to achieve the desired Mg/Al ratio in the stream, which results in the precipitation of LDHs (e.g. hydrotalcites) . Due to pre-existing alkaline conditions (pH of at least greater than 7 and preferably greater than 8) of alkaline mineral processing or metallurgical streams, in situ formation of LDH is advantageous when the desired Mg/Al ratio is achieved. As explained in Example 1, uranium-containing ores include a range of other elements present in addition to uranium, including heavy metals, metalloids and/or REEs. In situ formation of LDH materials also results in the incorporation of cations such as Ln ³⁺ cations and/or Ce ³⁺ and Ce ⁴⁺ and/or Eu ²⁺ or Eu ³⁺ oxidation states as well as a range of anions including oxometallic anions or oxygen-containing anion). Laboratory tests have demonstrated that it is preferable to add Al-containing compounds first or together with any Mg-containing compounds to prevent Mg precipitation as Mg carbonate compounds such as MgCO3 rather than for the formation of LDH.

The in situ formation of LDH also resulted in REE cations shown to be strongly partitioned into the main metal hydroxide layer of LDH. As mentioned previously, since uranium exists as an oxygen-containing cation generally called uranyl (UO ₂ ²⁺ ) cation, uranyl ions are too large to replace +2 cations such as Mg 2+ into LDHs. Alkaline earth and transition metals are usually present in the metal hydroxide layer of LDH. Again, under the basic conditions of the stream, anionic uranyl complexes are formed. At moderate to higher pH conditions of the stream, UO ₂ ²⁺ -CO ₃ ^2- anion complexes (e.g. UO ₂ (CO ₃ ) ₂ ^2- , UO ₂ (CO ₃ ) ₃ ^4- , CaUO ₂ ( CO ₃ ) ₃ ^2- ) can dominate. Considering this selective morphology of UO ₂ ²⁺ as anion complexes, these uranyl anion complexes preferentially partition into the anionic interlayer of the in situ formed LDH.

It is important to understand that under the reaction conditions of Example 3, as explained above, only the carbonate complex will predominate, and some REEs, especially the medium (MREE) and heavy REE (HREE) may be preferential remain in solution due to the known preferential complexation of MREEs and HREEs by carbonate ligands. Considering that MREEs and HREEs are generally considered to be the most valuable components of REEs due to their generally low abundance, this preferential form under alkaline conditions can be advantageously used.

In this specification and claims (if any), the word "comprise" and its derivatives include "comprises" and "comprising" include each of the stated integers, but do not exclude the inclusion of one or more additional integers .

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable combination or combinations.

Following the statute, the invention has been described in language of more or less specific structural or methodological features. It is to be understood that the invention is not limited to specific features shown or described, since the means described herein comprise preferred forms of carrying out the invention. Accordingly, the invention is claimed in any form or modification thereof within the proper scope of the appended claims, if any, duly interpreted by those skilled in the art.

quote

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Claims (40)

1. A kind of 1. anion thing for being used to handle the cationic substance containing one or more dissolvings and/or one or more dissolvings The method of the water of matter, this method comprise the following steps：

   (a) silicate material containing magnesium and/or aluminium is added in water, and the silicate material is dissolved in water by least a portion In, so as to which at least a portion magnesium and/or aluminium are leached into water from the silicate material；With

   (b) reaction condition is controlled, to reach for being formed in situ layered double-hydroxide the suitable Mg in water:Al ratios Rate, layered double-hydroxide contain the Mg and Al as main matter in LDH lattice；

   In the LDH that wherein at least one of the cation of the dissolving and/or anionic species manual reduction is formed.
2. 2. method according to claim 1, wherein the step of dissolving the silicate material containing magnesium and aluminium is included in condition of acidic pH Under from the silicate material leach magnesium and aluminium.
3. 3. method according to claim 1, wherein the step of dissolving the silicate material containing magnesium and/or aluminium is included in alkalescence condition Under from the silicate material leach aluminium.
4. 4. according to the method for any one of preceding claims, wherein the step of dissolving the silicate material is also included from the silicic acid Salt material leaches at least a portion silica.
5. 5. according to the method for any one of preceding claims, wherein dissolving step includes the silicate material in stirring water, To leach at least a portion magnesium and/or aluminium from the silicate material.
6. 6. according to the method for any one of preceding claims, wherein addition step includes addition contains magnesium and/or aluminium comprising described Silicate material and other silicate material mixture.
7. 7. according to the method for any one of preceding claims, wherein the step of controlling the reaction condition includes addition at least one Compound containing Mg and/or at least one compound containing Al are to reach for being formed in situ LDH the suitable Mg in water:Al ratios Rate.
8. 8. method according to claim 6, wherein at least one aluminum contained compound includes aluminate (Al (OH)₄Or AlO₂ ^- .2H₂) or aluminum sulfate, aluminium hydroxide or the organo-metallic compound containing aluminium O.
9. 9. according to claim 6 or the method for claim 7, wherein at least one compound containing Mg includes MgO or Mg (OH)₂Or its mixture.
10. 10. according to the method for any one of preceding claims, wherein the step of controlling the reaction condition is also used for including offer It is formed in situ LDH substantially alkaline reaction condition.
11. 11. according to the method for any one of preceding claims, wherein the step of controlling the reaction condition also include addition alkali or Sour neutralization materials are to be formed in situ LDH.
12. 12. method according to claim 10, wherein other alkali or sour neutralization materials are selected from one or more alkali or acid neutralizes Solute, slurry or solid material or its mixture, including lime, white lime, calcined magnesia, sodium hydroxide, sodium carbonate, carbonic acid Hydrogen sodium or sodium metasilicate.
13. 13. according to the method for any one of preceding claims, this method also includes removing the hydrotalcite being formed in situ at least The step of a part, wherein at least one of the cation of the dissolving and/or anionic species is included into the hydrotalcite or LDH In.
14. 14. according to the method for any one of preceding claims, the wherein silicate material includes one or more：Concave convex rod Stone；Clinoptilolite；Sepiolite；Talcum；The vermiculite mineral aggregation or homobium of rock formation, the flower of the rock such as grinding Gang Yan, greenstone or serpentinite, or coating, soil, deposit or waste material, such as come self-alumina refining (red mud) or coal combustion (flying dust).
15. 15. according to the method for any one of preceding claims, wherein the silicate material of at least a portion from step (a) The LDH formed with step (b) situ forms insoluble clay material mixture, and wherein the clay material mixture is included described The cationic substance of at least one or more of dissolving and/or the anionic species of one or more dissolving.
16. 16. according to the method for any one of preceding claims, wherein the undissolved clay material particle from step (a) carries For at least one of nucleation site for forming the LDH formed in step (b) situ.
17. 17. according to the method for any one of preceding claims, the cationic substance of the one or more dissolving in its reclaimed water Include magnesium and/or aluminium cations so that the lattice for the LDH that at least a portion manual reduction in the magnesium and/or aluminium of dissolving is formed In.
18. 18. according to the method for any one of preceding claims, at least one of anion of dissolving in its reclaimed water is network Close anion so that at least one of complex ion is inserted into the intermediate layer for the LDH being formed in situ.
19. 19. according to the method for any one of preceding claims, wherein the LDH being formed in situ includes hydrotalcite.
20. 20. according to the method for any one of preceding claims, this method be used to handle the metallicity complexing containing dissolving it is cloudy from The water of son and the cation of one or more dissolvings so that the metallicity complex anion is inserted into the intermediate layer of LDH materials, And wherein one or more other cations are included in the crystal structure or matrix of the LDH materials.
21. 21. method according to claim 20, this method also include the pH levels in control water so as to control be complexed in water it is cloudy from The step of form of son.
22. 22. according to the method for any one of claim 20 or 21, this method also includes separating LDH from the water of step (b), and Step is recycled from LDH intermediate layer recovery metallicity composition by being subjected to the LDH of separation.
23. 23. method according to claim 22, wherein the recycling step include ion-exchange step, the ion-exchange step Including adding at least one substituent anion into ion exchanged soln, and it is separated to ion exchanged soln introducing LDH so that the substituent anion replaces the complex anion of at least some insertions by ion-exchange mechanism, so as to cause this Complex anion is discharged into the ion exchanged soln from the intermediate layer of the LDH.
24. 24. method according to claim 23, the wherein ion-exchange step also include control pH conditions to promote the complexing cloudy Ion is from the displacement in the intermediate layer and/or promotes the complex anion of preferred type relative to the material shape of other complex anions Into.
25. 25. according to claim 23 or the method for claim 24, the wherein substituent reagent includes following one or more： NTA, EDTA, and/or wherein the substituent reagent have relative to the complex anion inserted in the LDH materials it is significantly more Electronegativity.
26. 26. according to the method for any one of claim 23 to 25, the wherein recycling step is additionally included in the ion-exchange step The LDH materials are separated afterwards.
27. 27. according to the method for any one of claim 20 to 22, the wherein recycling step includes being subjected to the LDH materials Heat treatment or thermal decomposition, are collapsed or the material of meta-stable so as to be formed.
28. 28. according to the method for the claim 27 when being subordinated to any one of claim 20 to 22, the wherein heat treatment step The LDH materials are caused to be recrystallized after thermal decomposition, so as to result in the first oxide material for including pre-selection metallicity composition With the second oxide material for including one or more other metals.
29. 29. according to the method for any one of claim 27 or 28, the wherein heat treatment is carried out under notable reductive condition.
30. 30. according to the method for any one of claim 27 to 29, this method be additionally included in before the heat treatment or thermal decomposition or Period adds other additive to the LDH materials.
31. 31. according to the method for any one of claim 27 to 30, wherein this method also include controlling the other additive with The ratio of the LDH materials, with the optionally formation of control oxide material in heat treatment or thermal decomposition.
32. 32. according to the method for any one of claim 20 to 31, the wherein recycling step includes optimizing the LDH materials Crystal structure or matrix, so that one or more other cations optionally to be included to LDH crystal structure in step (b) Or in matrix.
33. 33. according to the method for any one of preceding claims, the wherein complexing metal anion includes uranium or vanadium, and its In the one or more other metals include rare earth metal.
34. 34. according to the method for any one of claim 20 to 33, the wherein complex anion includes uranyl complex anion, example Such as UO₂(CO₃)₂ ^2-、UO₂(CO₃)₃ ^4-、CaUO₂(CO₃)₃ ^2-、UO₂(SO₄)₃ ^4-。
35. 35. according to the method for the claim 34 when being subordinated to claim 21, wherein controlling the pH of the solution that the uranium is determined The form of acyl complex anion.
36. 36. according to claim 34 or the method for claim 35, wherein by according to any one of claim 23 to 27 Ion-exchange step replaces inserted uranyl complex from LDH intermediate layer.
37. 37. according to the method for any one of claim 33 or 34, wherein making the LDH materials be subjected to according to claim 27 to 30 Heat treatment step so that the heat treatment by uranyl ion preferably for being reduced into U⁴⁺And/or U⁶⁺Notable reductive condition Lower progress.
38. 38. the method for any one of the claim 23 to 37 when according to claim 22 or being subordinated to claim 22, the party Method is further comprising the steps of：The LDH materials of the separation is contacted with the aqueous solution and this is dissolved into the LDH materials by least a portion In solution, so as to obtain the LDH dissolved in the solution and then control reaction condition in the aqueous solution, with from the LDH of dissolving Material in situ precipitates LDH materials so that and the complex anion is inserted into the intermediate layer for the LDH materials being formed in situ, and its Middle one or more other cations are included into the crystal structure or matrix for the LDH materials being formed in situ.
39. 39. according to the method for claim 38, wherein step LDH being dissolved in the aqueous solution includes controlling the aqueous solution PH preferably less than 7 and more preferably less than 5 and even more preferably less than 3 pH it is horizontal.
40. 40. according to claim 38 or the method for claim 39, wherein the step of controlling the reaction condition in the aqueous solution is wrapped Include and control the pH of the aqueous solution preferably horizontal in the pH more than 8.